Just going to add a few thoughts, based on what you've provided:
Now I am trying to decide if a subcompact will work and just rent a hoe for ditching and the abnormal work... not sure what that will be though.
Depending on the width/slope of the ditches desired, a tractor with a box blade can cut and maintain ditches. Unless large volumes of water need to be moved in a short time frame, shallower/wider ditches (like can be made with a tractor/box blade combo might be the better option) as the steeper the pitch the more erosion ability to maintain vegetation becomes an issue. So personally unless there are routine tasks that require a backhoe, it'd seem more cost effective to rent a excavator/track hoe as needed, and if the situation changes then consider adding a backhoe.
I have heard the snow fall will be from 1-4 feet.
Biggest thing here would be to decide how you want to handle it (or will be able to handle it). Snowblowers can move a lot of snow in a hurry, but the tend to require a fairly decent amount of HP per foot of working width ....and even then depending on how wet (or refrozen) the snow is a snowblower can become impractical. For example: snow with the consistency of Slushie being dropped by the clouds generally doesn't work all that well through a snowblower (especially in large amounts), how ever a light powdery snow will go though a snowblower quite nicely. .... (I grew up in MN, and spent a lot of time shoveling a rather long driveway by hand every winter).
There will be a spring or two to develop - want to make game watering stations and install a couple cisterns.
If these can/will be done multiple at a time, renting equipment would seem to make more sense.... which would also permit renting of a machine with longer/deeper reach than a tractor mounted backhoe.
Anything larger than a subcompact gets too tall and tippy I think.
I'd say that depends, just looking at a couple of different Kubota tractors the ratio of height to width made it apparent that a larger tractor can have the advantage in a couple of different ways. For example comparing the height/width ratio of a B50 series tractor to larger Grand L would indicate that (even at the minimum tread width on the Grand L) the Grand L has a shorter wider shape than a B50 series tractor. So adding wheel weights/or filled tires to help drive the center of gravity lower, and setting the rear tires to wider stance, would make for an even more stable platform. Granted on the other hand a large narrow bodied tractor (like Kubota's narrow M series) will be more of a vertical rectangle shape which would make it less stable.
That'd be the side-to-side stability, the length of wheelbase would affect the fore-aft stability as well as turning radius (for all fixed body/non-articulating tractors). A longer wheel base makes for more stability, and a larger turning radius (all other things being equal), where a shorter wheelbase would permit tighter turns (all other things being equal), but be less stable fore-aft. ...granted most tractors are going to be inherently more stable fore-aft than they are from side-to-side just due to their design.
Overall the size of the tractor should probably be more reflective of how quickly you want to perform a task, as the shape/layout/design of the tractor drives the stability more than size. The other thing to consider is the type of work to be performed is high HP needed, or is more weight needed for better traction in soil as most subcompact/compact tractors tend to be focused more on one vs. the other (most likely for cost reasons).
...just my :2cents: (which may or may not be worth that much).
